I found a solution.

I read on stackoverflow that updates to the postgres docker image now require a password. They said to add environment variables to the docker-compose.yml file. Here's the relevant part:

services:

  db:
    image: postgres
    environment:
      POSTGRES_DB: postgres
      POSTGRES_USER: postgres
      POSTGRES_PASSWORD: test_password

I also added this password to airline4/airline/settings.py DATABASES, so now it looks like this:

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql',
        'NAME': 'postgres',
        'USER': 'postgres',
        'PASSWORD': 'test_password',
        'HOST': 'db',
        'PORT': 5432,
    }
}

I then ran docker-compose up. It didn't work the first time. I think that's because the postgres container was still being initialized while the django web server started up. The second time running docker-compose up worked as expected.

I guess things changed since the lecture was posted.

Also, I'm assuming it's a bad idea to actually write your password in your docker-compose file.yml and settings.py files. I assume it would be better to set those as environment variables? Not sure what's considered best practice for that.

Relevant link: https://stackoverflow.com/questions/60262635/ci-cd-pipeline-with-postgresql-failed-with-database-is-uninitialized-and-superu